Paleoanthropology-Reconstruct anatomy, behavior, and environment of past hominins

-Includes locating early hominin sites, collecting faunal remains, and artifacts

-Something's date is younger/older than known dates

Stratigraphic dating-Principle that underlying layers are older than overlying layers

Strata: layers of Earth

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Relative dating

-Numerical dates (years, centuries, etc) within a margin of error

Radiometric dating-Unstable isotopes of an element decays into another element

Half-life: measurement based on time it takes an unstable element to decay into another element

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Absolute dating

Carbon dating (dates: 500-75 kya)-5730 year half-life

-Organic materials

-Dates archaeology/recent sites

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Radiometric dating

Potassium/Argon dating (dates: 100 kya-4.6 bya)-1.25 billion year half-life-Volcanism heats rock and releases argon. -Measure amount of Ar-40 in lava/ash = when it was last heated

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Radiometric dating methods

Earliest nonhuman primates resemble ancestral living primates

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Primate fossil record

Paleocene (65-56 mya)-Emerged soon after mammals -Found in North America, Europe, and Asia

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Nonhuman primate fossil record

Eocene (56-34 mya)-Radiation: 200 species emerged (similar to prosimians/tarsiers)-Most extinct by Late Eocene

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Nonhuman primate fossil record

Oligocene (34-23 mya) -Ancestors to modern monkeys

Fayum deposit-Many fossil primates

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Oligocene (34-23 mya)-Ancestors to modern monkeys

Aegyptopithecus-Largest Fayum anthropoid-Significant sexual dimorphism

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Oligocene (34-23 mya)-Ancestors to monkeys

Aegyptopithecus-Largest Fayum anthropoid

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Miocene (23-5 mya)-Golden age of apes (100s of ape species)-Warming trend begins

Proconsul (Africa)-Large-bodied

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Question: What's a hominin?Defining traits-Bipedal-Larger brains-Tool-making behavior

Mosaic evolutionary pattern-Evolution of some traits or functions differ in tempo

Bipedalism: defining hominin trait because the others underwent significant evolutionary changes later

Mosaic evolutionary pattern-Evolution of some traits or functions differ in tempo

Bipedalism: defining hominin trait because the others underwent significant evolutionary changes later

Bipedalism: defining Hominin feature

Hominin bipedalism differs from nonhuman primate locomotion:

Obligate bipeds: most efficient means of locomotion

Habitual bipeds: most common form of locomotion

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Question: Why be bipedal?

Best hypothesis: allows for more energetically efficient locomotion

Bipedal adaptation-Frees hands for carrying things, making/using tools-Bipedal stance gives a wider view of surrounding area-Bipedal walking = efficient way to cover long-distances

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Question: What are anatomical and structural changes in the fossil record showing bipedalism?

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Cranial-Foramen magnum-Spinal curve

Bipedalism - S-curve

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Evidence of bipedalism in the fossil record

PostcranialPelvis: bowl-shaped-Shorter, broader-Extended around the sides

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Evidence of bipedalism in the fossil record

Lower limbs-Long legs, short arms-Diagonal femur

-Provide stability

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Evidence of bipedalism in the fossil record

The foot-Foot arches-Foot stabilizes instead of grasping tree limbs

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Evidence of bipedalism in the fossil record

Pre-Australopiths (7-4.4 mya)

Sahelanthropus 7 myaCentral Africa-Well-preserved cranium-Small-brained (350 cm3) but flat-face

Bipedal?-Position of foramen magnum suggests bipedalism

Pre-Australopiths (7-4.4 mya)

Orrorin 6 myaEast Africa-First potential hominin postcranial remains

Bipedal?-Angle of femur bone suggests bipedalism

Pre-Australopiths (7-4.4 mya)

Ardipithecus5-4 myaEast Africa-Fragmentary to complete skeletons-Derived pelvis-CC = 350 cm3

Bipedal?-Probably but lived in woodland environment

Gracile australopithsAustralopithecus afarensis4-3 myaEast Africa-CC = 420 cm3

-3 ft tall-Ancestor to later hominins

Gracile australopithsAustralopithecus afarensis4-3 myaEast Africa -CC = 420 cm3

-3 ft tall-Ancestor to later hominins

Lucy-40% complete skeleton-Femur bone diagonal

Gracile australopithsAustralopithecus afarensisWhen: 4-3 myaWhere: East Africa (Laetoli for example)-CC = 420 cm3

-3 ft tall-Ancestor to later hominins

Laetoli footprints-Longer digits-Arches

Gracile australopithsAustralopithecus afarensisWhen: 4-3 myaWhere: East Africa (Laetoli for example)-CC = 420 c3-3 ft tall-likely ancestor to later hominins

Laetoli footprints-Longer digits-Arches

Gracile australopiths

Australopithecus africanus3-2 myaSouth Africa-CC = 440 cm3

Taung child

Robust australopiths = Paranthropus

Paranthropus2-1 myaEast and South Africa-Broad, flared-out cheekbones

Robust australopiths = Paranthropus

Paranthropus2-1 myaEast and South Africa-Broad, flared-out cheekbones

Sagittal crest: where jaw muscles attached on cranium

Robust australopiths = Paranthropus

Paranthropus2-1 myaEast and South Africa-Broad, flared-out cheekbones

Sagittal crest: area where jaw muscles attached on cranium

Specialized diet of tough, reedy plants-likely over-specialized and went extinct

Robust australopiths = Paranthropus

Paranthropus2-1 myaEast and South Africa-Broad, flared-out cheekbones

Sagittal crest: area where jaw muscles attached on cranium

Specialized diet of tough, reedy plants-likely over-specialized and went extinct

Early Homo (2.5-1.8 mya)

Homo habilis "Handy-man" 2.5-1.8 myaEast Africa-CC = 630 c3 (20% increase in brain size)

-First hominin associated with stone-tools

Oldowan tool industry (2.6 mya)

-Earliest stone tool industry-Associated with Homo habilis

Flakes -Used to butcher-Disposable

Choppers-Crack bones for marrow

Oldowan tool industry (2.6 mya)

-Earliest stone tool industry-Associated with Homo habilis

Flakes -Used to butcher-Disposable

Choppers-Crack bones for marrow

Early hominins in general

Early hominin derived traits-All bipedal-Genus Homo stone-tool use

Mostly ancestral -smaller-bodies, bigger teeth, smaller brains-tied more to arboreal lifestyle-ape-like accelerated growth and development

Early hominins

Gracile: small-boned or of slight build Refers to characteristics seen in the skull of Australopithecus africanus. A. africanus is similar in some ways to the "robust" species, but lacks their cranial and mandibular adaptations to a dry, hard to chew diet. The characteristics of the "gracile" australopithecines are believed to reflect their diet of softer, easier to chew food items such as fruit, young leaves, and insects.

Early hominins

Robust: Heavier, thick bones and muscles. Refers to characteristics seen in the skulls of three hominin species - Paranthropus aethiopicus and Paranthropus boisei from East Africa, and Paranthropus robustus from South Africa. The characteristics include huge molars and "molarized" premolars, broad cheeks with large zygomatic arches that allow passage of large chewing muscles, and a sagittal crest for attachment of those muscles on the relatively small cranium. The characteristics of the "robust" species are believed to reflect their diet of dry, hard to chew food items such as nuts, roots, tubers, etc.

Gracile: small-boned or of slight build Refers to characteristics seen in the skull of Australopithecus africanus. A. africanus is similar in some ways to the "robust" species, but lacks their cranial and mandibular adaptations to a dry, hard to chew diet. The characteristics of the "gracile" australopithecines are believed to reflect their diet of softer, easier to chew food items such as fruit, young leaves, and insects.